1. Field of the Invention
The present invention relates to monitors, and more particularly, to monitor controllers.
2. Description of the Prior Art
In an interlaced scan signal, each frame includes an odd field and an even field respectively having a plurality of odd scan lines and a plurality of even scan lines. Within the scan lines, the portion constituting display data, or active data, corresponds to an image displayed with rows of pixels of a video display device. Taking an NTSC system as an example, as is well known in the art, one of the odd field and the even field has one scan line more than the other. Therefore, as the vertical sync (VS) signals are sampled and synchronized according to the horizontal sync (HS) signals, a digital display signal generated after receiving and decoding a source signal will result in a VS signal having a one-scan-line time difference between a pulse interval corresponding to the odd field and a pulse interval corresponding to the even field.
In subsequent processing of the digital domain, for example, interpolation or other operations, a VS signal before processing is usually referred to as the input vertical sync (IVS) signal, and a VS signal after processing is usually referred to as the output vertical sync (OVS) signal or the destination vertical sync (DVS) signal. For typical video processing, in order to achieve normal video display without utilizing excessive memories to perform buffering of input/output (I/O) frames, the OVS signal is typically controlled to be synchronous with the IVS signal. Therefore, the aforementioned phenomenon of the difference between the pulse interval corresponding to the odd field and the pulse interval corresponding to the even field propagates from input to output. In this situation, some display panels probably cannot display normally due to incompatibility problems.
In addition, within each frame, the odd scan lines in the odd field and the even scan lines in the even field respectively correspond to different locations of the image of the frame. For example, in the image of the frame, the first scan line of the even scan lines is located under the first scan line of the odd scan lines, and the second scan line of the odd scan lines is located under the first scan line of the even scan lines, and so on. However, as is well known in the art, performing video processing operations with the data of the odd field and the data of the even field in the same way will introduce vertical jittering to the images.